Reactor for contacting gases and a particulate solid

ABSTRACT

The present invention is a reactor that consists of a single shell that contains a reaction zone and a regeneration zone. The reaction zone and regeneration zone are arranged in such a manner that (a) a particulate solid may be transferred by flow of gases from the regeneration zone to the reaction zone by a first route and then back to the regeneration zone by a second route; and (b) the gases passing through the regeneration zone are not transferred to the reaction zone and the gases passing through the reaction zone are not transferred to the regeneration zone.

This is a division of application Ser. No. 758,607, filed Jan. 12, 1977,now U.S. Pat. No. 4,152,393, issued May 1, 1979.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 3,669,877 shows a separated reaction zone and oxidationzone. Open contact between the regeneration zone and the reaction zoneof the reactor in this patent, however, does not prevent the mixing ofgases in the oxidation and regeneration zones. As a consequence, thereaction product is contaminated with the gases from the regenerationzone. The present invention essentially eliminates this contamination.

Also, U.S. Pat. No. 3,669,877 does not provide an orderly transfer of asolid particulate from the reaction zone to the regeneration zone andback to the reaction zone. In contrast, the present invention providesan orderly and continuous flow of the solid particulate through thereaction zone and the regeneration zone. This continuous flow isaccomplished without the transfer of gases between the two zones.

SUMMARY OF THE INVENTION

A new reactor has been discovered in the present invention. This reactorconsists of an outer shell that contains a first contact zone called areaction zone and a second contact zone called a regeneration zone, saidreaction zone and said regeneration zone being arranged in such a mannerthat (a) particulate solid may be transferred by the flow of gases fromthe regeneration zone to the reaction zone by a first route and back tothe regeneration zone by a second route; and (b) the gases passingthrough the regeneration zone are not transferred to the reaction zoneand the gases passing through the reaction zone are not transferred tothe regeneration zone. The reactor of the present invention may be usedin one embodiment for a reaction that employs a particulate solid thatis capable of retaining certain elements of the gas stream in one zoneand relinquishing those elements in another zone. For example, in theoxidation of propylene to acrolein, an appropriate catalyst could beoxidized in a regeneration zone by acquiring and retaining oxygen fromair, and in the reaction zone, a feed consisting of propylene isintroduced, and the catalyst relinquishes its retained oxygen, oxidizingpropylene to acrolein. The reactor effluent contains only unreactedpropylene and products, whereas in the art reactions, large amounts ofinert gases are part of the effluent. In a similar manner, copper oxidecould be reduced to copper metal with a stream of hydrogen in aregeneration zone and then the reduced copper oxide could be transferredto the reaction zone where the reactant is reduced and the reducedcopper oxide is oxidized.

The present invention is best understood by reference to the drawing.

DESCRIPTION OF THE DRAWING

FIG. 1 shows the cross-sectional side view of the reactor.

FIG. 2 shows the top view of the same reactor.

Referring to FIG. 1, it is seen that the reactor consists of an outershell 1 which is a cylinder having a bottom. The outer shell 1 has a top2 with a downwardly extending concentric wall 3. In the broaddescription of the invention, top 2 but not concentric wall 3, is a partof the enclosed outer shell. The zone inside of concentric wall 3 is theregeneration zone, and the zone outside of wall 3 is the reaction zone.Cyclone 4 is used for the regeneration zone, and cyclone 5 is used forthe reaction zone.

Inside the shell 1 there is concentric wall 6 and concentric wall 7having substantially the same height. These two concentric walls in thereactor are connected around the bottom. These walls prevent the mixingof gases from the reaction zone and the regeneration zone while allowingsolid to be transferred from one zone to the other.

As indicated above, shell 1, and walls 3, 6 and 7 are cylindrical andconcentric with one another. It should therefore be appreciated thatshell 1 and walls 3, 6 and 7 are "similar" in the geometric sense.

There is a reactant feed inlet 8 through which reactants are fed intothe reactor around the circumference at the bottom between concentricwalls 6 and 7. Regeneration air is fed through inlet line 9 and aplurality of nozzles located radially around the circumference of thebottom. This regeneration air feed acts as a pump in this particularreactor by drawing the particulate solid out of the reaction zone andtransferring it to the regeneration zone.

In addition to the above components, the reactor has various aeratorinlets where small amounts of a gas are fed into the reactor toencourage movement of the particulate solid. These aerators 10, 11 and12 distribute the gas throughout the circumference of the reactor andare placed in positions where the particulate solid tends to becomeimmobilized.

In the operation of the reactor, the total reactor is filled with aparticulate solid to a level above the tops of walls 6 and 7. Theparticulate solid usually has a diameter of less than about 400 micronsfor metal oxide solids.

A small air or steam flow is begun through aerators 10, 11 and 12. Thisflow of gas is not sufficient to cause substantial movement of theparticulate solid. Regeneration air is then introduced through line 9.This flow of air acts as a pump and causes the particulate solid to moveinto the regeneration zone within wall 6 and to become fluidized.Simultaneously, with the beginning of the regeneration air, the reactantfeed can be started by passing the reactants into the reactor throughline 8.

In the operation of the reactor, the regeneration air passes through theparticulate solid oxidizing the solid and then the gas stream remainingis passed through cyclone 4 and out of the regeneration zone. Little orno gas is transmitted through any passage other than the cyclone underproper operating conditions.

In the reaction zone, reactant gas is passed into the reactor throughinlet 8, the reactants pass through the oxidized catalyst reacting inthe process to form the desired product, and all gas from the reactionzone passes from the reactor through cyclone 5. Little or no gas passesfrom the reaction zone to the regeneration zone under proper operatingconditions.

In the operation of the reactor, the flow of solids through theregeneration zone and the reaction zone is controlled by the flow ofgases and the pressures in the two zones. Following the path of theparticulate solid from the regeneration zone to the reaction zone andback, it is seen from the drawing that the catalyst begins its movementinside of the concentric wall 6. The particulate solid is carried by theair upward inside of wall 6 and over the top of wall 6. The solid thentravels down between wall 6 and wall 3. Gas supplied through aerator 11facilitates this movement of the solid down between wall 6 and wall 3.When the solid passes spacing 13, it enters into the reaction zone.

The primary reaction zone is formed between wall 3 and wall 7. In thiszone, reactant gases from reactant feed 8 cause the solid to move upwardand over wall 7 into the zone between wall 7 and the reactor shell 1. Inthis zone between wall 7 and the reactor shell 1, the solid movesdownward with the assistance of a gas stream from aerator 12.

As the particulate solid moves downward past aerator 12, it becomessubject to the pumping action of regeneration air through line 9.Pumping action is achieved by manifolding the regeneration air to amultiplicity of nozzles which act as ejectors utilizing the regenerationair as the motivating fluid. This pumping action draws the catalyst downunderneath the connection between walls 6 and 7 and sends it through theregeneration zone inside wall 6. Gas from aerator 10 is instrumental infacilitating this transfer of solid. Thus, the cycle of the particulatesolid is complete.

Referring to FIG. 2, a top cross-sectional view taken alongcross-sectional line 2 is shown. In this view, it is seen that thereactor of the invention consists of a numer of concentric walls.Concentric wall 6 is the innermost wall, cross-hatched wall 3 is next tothe outside. The solid line just outside of wall 3 shows that aerator 11extends around the circumference of wall 3.

Wall 7 is the next outer wall. Outer shell 1 is cross-hatched and theadjacent solid line on the outside shows that aerator 12 extends aroundthe circumference of shell 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

High rates of solid circulation can be obtained using this inventionwhile at the same time little or none of the gases in the two zones ofthe shell are mixed with each other. This circulation action providesenough catalyst in an oxidation, ammoxidation or oxidativedehydrogenation reaction to permit running a feed of pure reactants intothe reaction zone without the addition of air. For example, in theoxidative dehydrogenation of butenes to butadiene, the reactant feedcould be limited to the butene, thus eliminating the air that isnormally required. The ramifications of this elimination are verysignificant. In the oxidative dehydrogenation of butene using air, theair-to-butene ratio is normally about 10/1. In the present invention,the total of 11 volumes of gas that is required in the reaction zone isreduced to one volume. Only the butene is fed, and the 10 volumes of airin the reaction zone are eliminated. Thus the gas fed to the reactionzone for a given amount of capacity can be dramatically reduced.Moreover, the unreacted reactants for recycle and the desired productneed be separated only from the by-products rather than the large volumeof gas remaining in a normal oxidative dehydrogenation.

The reactor of the present invention may have the design shown in thedrawing, or it may have any other design in a single shell which meetsthe criteria of the present invention: (a) that a particulate solid maybe transferred from the regeneration zone to the reaction zone by afirst route and back to the regeneration zone by a second route; and (b)that the gases passing through the regeneration zone are not transferredto the reaction zone and the gases in the reaction zone are nottransferred to the regeneration zone.

The particular reactor geometry and the distribution and shape of thegas feeds may vary substantially. The contact zones may be open or theycould contain cooling coils or sieve trays or any other internalmodifications. The detailed design of the pumping system is primarilydependent upon the reactor design, the desired solids circulation rateand the pressure differential in the contact zones.

The reactor can be constructed of essentially any material. Choice ofmaterials is limited only by the nature of the reaction being conducted.Normally, metal reactors are used, but glass or clear plastic models aremost helpful for determining the flow rates of solids in the reactor andoptimum operation of the reactor. Clear models are also very useful forobserving whether "dead" spots are present. Solid that does notcirculate in the reactor is unavailable for the desired reaction.

In the practical operation of the reactor of the present invention, thecritical variables are: (1) the flow of gases through the reactor; and(2) the differential in the pressure between the reaction zone and theregeneration zone.

Gas flows in the reactor are characterized by the different compositionsof the gas and the different purpose of the flow.

The composition of gas flowing through the reaction zone and theregeneration zone is almost always different. Accordingly, the flow rateand direction of the flow should be adjusted so that the mixing of thegases of different composition is minimized. Using this criterion, aflow of the reactant propylene in the oxidation of propylene to acroleinwould not be directed in a manner that the propylene would escape thereaction zone and be combined with the gases in the oxidation zone.

The purpose of the flow of gas also differs. The flow of gas from aparticular gas inlet can be used to provide for movement of theparticulate solid through the communicating passageways, or it can beused to provide fluidization for the particulate solid. The maindifference between these two flows is the velocity of the gas. Thevelocity of the gas that provides transfer of the solid is substantiallyhigher than the velocity of the gas that provides fluidization.

The transfer of solids throughout the reactor is normally accomplishedby high velocity gas flows directed in the desired path of flow.Conveying the particulate solid around corners in the reactor, however,is most conveniently accomplished by eduction where the particulatesolid is drawn from one portion of the reactor and transferred throughan angular channel to another portion of the reactor. Referring to FIG.1, the eduction is provided by the regeneration air pumped through 9.This regeneration air draws the particulate solid from the reaction zoneand transfers it around a corner to the regeneration zone.

The gas flow of the aerators is to maintain fluidization and is alsoimportant. Increased fluidization by means of aerators should beprovided in areas where the particulate solid does not follow astraight-line path and in areas where the particulate solid traverses anarrow passageway. It has been found that increased fluidization isespecially important in areas where eduction takes place. Referring toFIG. 1, this fluidization is provided by aerator 10. The dramatic impactof the fluidization of this eductor is shown in the SpecificEmbodiments. In Table I, Examples 7-9 show the effect of differentdegrees of fluidization on the solids turnover rate. As the flow of gasthrough the aerator is increased, the solids turnover is increased.

In a particular reactor, the desired rate of flow of gases through thereaction zone and the regeneration zone is directly dependent upon thesize of the particulate solid needed and the circulation rates required.For any given reaction, catalyst and reactor the desirable flow ratescan be readily determined by observation in a clear plastic model or bya minimal amount of experimentation.

The second critical variable in the control of solids flow through thereactor is the pressure differential between the pressure in the gasphase of the regeneration zone as compared to the pressure in the gasphase of the reaction zone. This pressure differential is expressed asfollows:

    ΔP=P regeneration-P reaction

and is stated in terms of inches of water in view of the sensitivity ofthe solids circulation to this variable. The optimum pressuredifferential is just on the positive side of 0. As the pressuredifferential is decreased from a large positive value, the circulationof solids is increased. The circulation of solids should be maximized ata near zero value. As the pressure differential becomes negative, solidcirculation is again decreased and finally stops. Negative pressuredifferentials, however, are undesirable because this means that the gaspressure in the reaction zone is higher than the gas pressure in theregeneration zone. This negative pressure differential causes reactantsand products in the reaction zone to be transferred to the regenerationzone where these valuable gases are lost. To assure that no product islost, a slight positive pressure differential is preferably maintained.

The maximum ΔP that can be tolerated is a function of the reactorconfiguration, the strength and efficiency of the pump and the depth ofthe particulate solid in the reactor. Projecting from the small scale ofthe reactors presently used, it is believed that the ΔP would preferablyfall within the range of ±150 inches of water. In the most preferredpractice of the invention, the ΔP would be between about 0 and about 150inches of water.

The flow of gases through the reactor and the pressure differentialdiscussed in detail above, are the critical variables in the operationof the reactor. Other factors that control the operation of the reactorare best adjusted by experimentation with a clear plastic model.

The solid circulation rates obtainable by the reactor of the presentinvention are surprisingly high. For example, in a small reactor havinga catalyst inventory of only about 6 pounds, circulation rates of wellover 300 pounds per hour were easily obtained.

The flow of gases through the reactor should be controlled in such amanner that large bubbles of gas in the solid are minimized. Such largebubbles do not have adequate contact with the solid to allow aneffective gas-solid reaction to occur. Most preferred are gas flow ratesthat cause even and continuous flow of the solid particulate from onezone to the other.

Passing of gases between the reaction zone and the regeneration zone isundesirable in the present invention. As noted, proper operation of thereactor of the invention does not permit the passage of gases from onesection to the other. Yet, some solids adsorb gases in one section ofthe reactor and desorb these gases in the other section of the reactor.Thus, even though no gases as such are transferred from the reactionzone to the regeneration zone, there is a mixing of the reactants andregeneration gases due to adsorption of the gases on the solid. Thisproblem may be at least partially rectified by contacting the solid witha gas that desorbs the adsorbed gases as the solid passes from one zoneto another. For example, steam could be contacted with the catalyst usedin an ammoxidation reaction just as the catalyst leaves the reactionzone. Gaseous reactants and products adsorbed on the catalyst aredesorbed by this treatment, and the presence of reactants and productsin the regeneration zone is minimized.

The reactor can be used for essentially any situation where gas iscontacted with a particulate solid. Preferred is the use of the reactorin solid-gas reactions where the particulate solid is able to acquireand retain a component of one gas stream and then relinquish thatcomponent in a second gas stream. Reactions of most interest in thepresent invention are the oxidation, ammoxidation and oxidativedehydrogenation of hydrocarbons of up to about 20 carbon atoms. Thesereactions with olefins of 3 to 5 carbons and alkylbenzenes are ofgreatest interest. In these reactions as noted above, reaction isconducted using the oxygen retained in the oxidized catalyst rather thanthe addition of air as a reactant. Using this reactor, substantialsavings are realized in the space for reaction zone and in the recoveryand purification systems.

SPECIFIC EMBODIMENTS The Reactor

A reactor was constructed of clear plastic tubing according to thedesign of the drawing. The shell was a tube of 6.50 inches outsidediameter and 5.75 inches inside diameter. The wall adjacent to the shell(wall 7 of the drawing) extending upward had an inside diameter of 5.00inches and an outside diameter of 5.25 inches. The next adjacent wallextending downward from the top (corresponding to wall 3 of the drawing)had an outside diameter of 4.00 inches and an inside diameter of 3.75inches. The next adjacent wall (corresponding to wall 6 of the drawing)extending upward from the bottom and connected to the other wallextending from the bottom had an inside diameter of 3.00 inches and anoutside diameter of 3.25 inches so long as it runs parallel down alongthe next adjacent outer wall, and then an outside diameter of 4.00inches beyond the length of the downward extending wall. The overallinternal height of the reactor was 24 inches. The top of the reactionzone and the regeneration zone contained filters made of sinteredstainless steel.

The air for the regeneration zone was fed through a feed linecorresponding to 9 of the drawing. In this position, the regenerationair is a pump and is referred to in the examples as the pump. Likewise,the aerator 10 will be referred to as the pump aerator. The pump aeratorhead and reactant feed head were sintered stainless steel.

The reaction zone and regeneration zone downflow aerators consist of ahollow ring with 0.013-inch diameter drilled holes spaced 5/8 inchapart. The regenerator air was fed through a pump system which was 30tubes or nozzles spaced radially around the circumference of the reactorat essentially equal intervals. These tubes were 1/16 inch outsidediameter, 0.045 inch inside diameter and 11/8 inch long and wereconnected to a common gas supply.

EXAMPLES 1-12 Effect of gas flow rates on solids turnover.

The reactor was filled with 2950 g. of a solid metal oxide that had aparticle size between about 44 and about 177 microns. The spacingbetween the regeneration zone and the reaction zone, spacing 13, wasadjusted to 0.75 inch.

The reactor was run at various gas flow rates for the pump, the reactorand the pump aerator. The regeneration aerator (corresponding to 11 ofthe drawing) was run at 2.2 ft.³ /hr., and the reactor aerator(corresponding to 12 of the drawing) was run at 2.6 ft.³ /hr. Air wasused as feed through all inlets of the system.

The solids turnover rate was measured by visual observation of the rateof downflow of solid in the chamber closest to the shell. From this rateof downflow plus knowledge of the volume in this outside chamber and thedensity of the solid, the solid turnover rate was calculated. At givenflow rates, the values obtained were reasonably reproducible. Theresults of these various air flow rates at a ΔP of 0 in. H₂ O are shownin Table I.

                  TABLE I    ______________________________________    Turnover Rate for Various Flows    Flow Rates, ft..sup.3 /hr.                              Pump   Solids Turnover    Example Pump    Reactor   Aerator                                     Rate, lb./hr.    ______________________________________    1       36      12.4      1.5    0    2       60      12.4      1.5    34    3       80      12.4      1.5    57    4       100     12.4      1.5    109    5       80      12.4      3      149    6       80      21.1      3      220    7       80      37        3      283    8       80      37        1.5    176    9       80      37        4.5    315    10      80      12.4      4.5    142    11      36      37        1.5    34    12      100     37        1.5    202    ______________________________________

EXAMPLES 13-15 Solids turnover at narrower spacing between zones

The spacing 13 between the regeneration zone and the reaction zone wasnarrowed from 3/4 inch to 1/4 inch. The effect on solids flow at a ΔP of0 in. H₂ O is shown in Table II. The flow of gas through the pump wasmaintained at 80 ft.³ /hr. and flow through the pump aerator was 3.0ft.³ /hr.

                  TABLE II    ______________________________________    Effect of Change in Spacing Between Zones    Gas Rate           Solids Turnover, lb./hr.    Example of Reactor, ft..sup.3 /hr.                           1/4" spacing                                      3/4" spacing*    ______________________________________    13      12.1           100        149    14      20.8           140        220    15      36             180        283    ______________________________________     *At closest reactor gas flow rate from Table I

EXAMPLES 16-22 Effect of pressure differential on solids turnover

The pressure in the gas phase of the regenerator less the pressure inthe gas phase of the reactor has been defined as ΔP or the pressuredifferential. As noted, this pressure differential has a substantialimpact on the solids turnover.

To obtain these data, the reactor was run under the following gas feedrates: pump 80 ft.³ /hr., reactor 30 ft.³ /hr. and pump aerator 3 ft.³/hr. The pressure in the regeneration zone was then varied byrestricting flow of air through regeneration zone exit causing anincrease in the pressure of the gas phase in the regeneration zone andthe consequent positive ΔP. The effect of different ΔP values is shownin Table III.

                  TABLE III    ______________________________________    Effect of Δ P on the Solids Turnover                           Solids Turnover    Example     ΔP, in. H.sub.2 O                           Rate, lb./hr.    ______________________________________    16          0          259    17          1.0        202    18          1.5        151    19          2.0        130    20          3.0        95    21          4.0        72    22          5.0        70    ______________________________________

It can be seen from Table III that optimum solids turnover is obtainedat a ΔP of zero. It will be remembered, however, that the ΔP valueshould remain on the positive side to prevent the transfer of gases fromthe reaction zone to the regeneration zone.

EXAMPLES 23-31 Gas leakage between zones at various flow rates

To determine the disposition of gases fed into the reactor, air was fedthrough all gas input lines except one. In this one line, CO₂ was fed,the effluents of both zones were then analyzed for CO₂. The gasdistribution is defined at that percent of the CO₂ going to theregeneration zone or the percent of CO₂ going to the reaction zone froma given inlet.

At a ΔP of 0 in. H₂ O the reactor was run at various solid turnoverrates using a 3/4 inch spacing 13 between zones while CO₂ was injectedat different places. The results of these tests are shown in Table IV.

                  TABLE IV    ______________________________________    Distribution of Gases Fed to Reactor                   CO.sub.2    Solid Turnover Injection                            Gas Distribution, %    Example           Rate, lb./hr.                       Point    Reaction                                        Regeneration    ______________________________________    23     34          Pump     0.05    n.d.    24     34          Reactor  n.d.    16.7    25     34          Pump     50.5    49.5                       Aerator    26     149         Pump     0.9     n.d.    27     149         Reactor  n.d.    15.5    28     149         Pump     92.4    7.6                       Aerator    29     314         Pump     0.5     n.d.    30     314         Reactor  n.d.    0.5    31     314         Pump     14.7    85.3                       Aerator    ______________________________________     n.d. = no data (it is assumed that the remainder to make 100% went to thi     zone).

EXAMPLES 32-33 Reactor to regenerator leakage using a 1/4 inch spacingat various flow rates

Using a 1/4 inch spacing between the regeneration zone and the reactionzone rather than the 3/4 inch spacing of Examples 23-31 above, gasleakage from the reactor feed to the regenerator were determined at theflow rates of Examples 13 and 14. The gas leakage from the reaction zoneto the regeneration zone using a flow rate of 100 lbs./hr. (Example 13)was 5.1% at a ΔP of 0. At a flow rate of 140 lbs./hr. (Example 14) thegas leakage was 1.6%.

EXAMPLE 34 Effect of ΔP on gas leakage

The reactor was run under steady conditions at a ΔP of zero. The gasleakage from the reactor to the regenerator from the CO₂ being fed intothe reactor was 8.2%. The ΔP was raised to one inch of H₂ O, and theleakage was reduced to 3%.

EXAMPLE 35 Ammoxidation of propylene using oxidant reactor

A metal reactor as described above was constructed. A fluid bed oxidanthaving the composition 50% K₀.1 Ni₂.5 Co₄.5 Fe₃ BiP₀.5 Mo₁₂ O_(x) wherex is the number of oxygens to satisfy the valence requirements of theother elements present, and 50% SiO₂ was used as the particulate solid.The oxidant had a particle size between 74 and 177 microns.

To the reactor was added 2875 g. of the oxidant. This amount of catalystcovered the upward extending walls by about 1/4 inch. Under a continuousflow of air through the reactor, regenerator air inlet and reactantinlet and flow of steam through all three aerators, the temperature ofthe reactor was brought to 523° C.

At reaction temperature, the catalyst turnover was 90,800 g./hr., thepump feed rate was 90.8 ft.³ /hr., the pump aerator feed rate was 4.3ft.³ /hr. and the reactor feed rate was 20.3 ft.³ /hr. In addition, avery slow feed of steam was maintained to the other two aerators. The ΔPof the reactor was 0.5±0.5 in. H₂ O.

Under these steady-state conditions, the feed of air to the reactor wasswitched to a mixture of propylene and ammonia in the ratio of 1:1.2.The reaction zone effluent was recovered and analyzed. The % conversionof the propylene is stated as the amount of propylene reacted over theamount fed times 100. The % selectivity is the amount of acrylonitrileformed over the amount of propylene reacted times 100. The % per passconversion is the product of the percent conversion times the percentselectivity divided by 100.

The % conversion of the propylene was 89.0%, the selectivity toacrylonitrile was 64.4% and the per pass conversion to acrylonitrile was57.3%. The effluent of the regeneration zone was analyzed for productsand reactants of the reaction. Only a trace of organic compounds wasfound in this regeneration zone effluent.

EXAMPLE 36 AND COMPARATIVE EXAMPLE A Comparison of effluent from art toeffluent of the invention in ammoxidation

The composition of the effluent from the ammoxidation reactor of Example35 is compared in Table V to the composition of the effluent whenpropylene, ammonia and air are fed into the reactor in a ratio of1:1.1:10 over a catalyst to obtain a 97.3% conversion of the propylene,a selectivity for acrylonitrile of 68.7 and a total per pass conversionto acrylonitrile of 66.8%. These data show that in the dry reactoreffluent, the concentration of the desired acrylonitrile product isincreased more than fivefold as compared to the art. Recovery of theacrylonitrile from this more concentrated stream is much moreconvenient.

                  TABLE V    ______________________________________    Effluent Gas Comparison           Concentration of Gas in Dry Effluent, Mole %             Comparative Example A                              Example 36    Gas      (Art ammoxidation)                              (Oxidant of Invention)    ______________________________________    Acrylonitrile             6.3              34.3    Acetonitrile             0.2              5.1    Propylene             0.3              3.7    HCN      0.6              0.7    NH.sub.3 0.1              11.7    O.sub.2  1.5              0    N.sub.2  86.0             10.7    CO       1.8              4.1    CO.sub.2 3.1              29.1    ______________________________________

In the same manner as shown by the example above, other catalyticreactions can be conducted using this catalyst. For example, propylenecan be converted to acrolein or acrylic acid; butene can be converted tobutadiene; p-xylene can be converted in the presence of ammonia toterephthalonitrile; alkanes, such as propane, butane or isopentane canbe converted to olefins; ethylbenzene can be converted to styrene;methanol can be converted to formaldehyde; o-xylene can be converted tophthalic anhydride; ethylene or propylene can be converted to thecorresponding oxide; coal could be gasified; or solids could beretorted. In addition to these uses, any other solid-gas reation can beconducted where the solid is capable of acquiring components of a gas inone zone, retaining those components while being transferred to a secondzone and relinquishing those components in the second zone to adifferent gas stream.

We claim:
 1. A process for effecting separate and successive contact ofa particulate solid with a first gas stream and a second gas streamwithout substantial mixing of said gas streams comprising:establishing aparticulate solid flowpath for continuous recirculation of particulatesolid, said flowpath having in order a first upleg, a first downleg, asecond upleg, a second downleg and a return leg for returningparticulate solid from said second downleg to said first upleg, flowingsaid first gas stream upwardly through said first upleg so as tofluidize the particulate solid therein and elevate the particulate solidtherein to a first junction between said first upleg and said firstdownleg, withdrawing said first gas stream from above said firstjunction so that particulate solid above said first junction fallsthrough said first downleg and into said second upleg, flowing saidsecond gas stream upwardly through said second upleg so as to fluidizethe particulate solid therein and elevate the particulate solid thereinto a second junction between said second upleg and said second downleg,and withdrawing said second gas stream from above said second junctionso that particulate solid above said second junction falls through saidsecond downleg and into said return leg for return to said said firstupleg.
 2. The process of claim 1 wherein said first downleg isessentially annular in configuration and surrounds said first upleg,wherein said second upleg is essentially annular in configuration andsurrounds said first downleg, and wherein said second downleg isessentially annular in configuration and surrounds said second upleg. 3.The process of claim 2 wherein said first gas is supplied to said firstupleg from said return leg so that particulate solid in said seconddownleg is returned to said first upleg by induction.
 4. The process ofclaim 2 wherein the pressure difference between the pressure of saidfirst gas stream and said first upleg and the pressure of said secondgas stream and said second upleg is ±150 inches of water.
 5. The processof claim 4 wherein said pressure difference is about 0 to 150 inches ofwater.
 6. The process of claim 5 wherein said pressure difference isabout 0 inches of water.
 7. The process of claim 4 wherein saidparticulate solid is a catalyst.
 8. The process of claim 1 wherein saidfirst upleg is separated from said first downleg by a cylindrical walland wherein said second upleg is separated from said second downleg by acylindrical wall.
 9. The process of claim 8 wherein the cylindricalwalls are concentric.